Highlighting background triggered from a 3d model

Hi Guys,

I am fairly new to unity and am trying to figure out how to trigger a game object (this has the highlight script) that highlights itself. Right now the problem is that when i hover over the gem (3d model) i don't trigger the game object that highlights itself (grid tile).

[file A]

At present the gem is highlighted like this:

 public void Highlight()
 {
     m_isHighlighted = true;
     renderer.material.color = m_highlightColor;
 }

This just highlights the gem, but I want to highlight its background.

I made another game object and place it on the current tile and added this highlight script to it:

[File B]

 using UnityEngine;

using System.Collections;

public class HighlightTile : MonoBehaviour {

 private float blueMultiplier = 3.50f;
 private float redGreenMultiplier = 0.50f;
 private Color originalColor;
 
 // Use this for initialization
 void Start () {
    originalColor = gameObject.renderer.material.color;
 }
 
 void OnMouseEnter()
 {
     AddHighlight();
 }
 
 void OnMouseExit()
 {
     RemoveHighlight();
 }

 public void  AddHighlight() 
 {
     float red = originalColor.r * redGreenMultiplier;
     float blue = originalColor.b * blueMultiplier;
     float green = originalColor.g * redGreenMultiplier;

     gameObject.renderer.material.color = new Color(red, green, blue);
 }

 public void RemoveHighlight()
 {
     gameObject.renderer.material.color = originalColor;
 }

}

Ideally I would like to highlight the gem and the grid in the background. Any feed back is appreciated, thanks